Members of Parliament tonight overwhelming endorsed historic legislation that will give gay couples the equal right to marry.

Almost half a century after homosexuality was legalised in Britain the House of Commons voted by a majority of 400 to 175 to redefine marriage and make it available to all.

But embarrassingly for David Cameron he failed to get a majority of his own MPs to support the move. 139 Tories, including two cabinet ministers, rebelled against the Government with just 132 supporting the measure. There were 75 abstentions.

Katherine, the House of Lords can in theory reject the bill, but is unlikely to do so. Even although the largest group there are crossbenchers, ie independents, there is a deeply held tradition that the peers only vote down the legislation of the lower house if it contravenes the constitution. You might be surprised to hear that we have one; it is ‘unwritten’ ie has accrued by convention, precedence and recognition.

Addendum: of course, Katherine, the Queen could in theory refuse to sign the act which brings the legislation into law. But the monarch would never act contrary to parliament’s expressed wishes. In cases like this her largely symbolic role as governor of the Church of England is meaningless.